In the 14 days before illness onset, 71% of case-patients and 74% of control- participants reported always using cloth face coverings or other mask types when in public.
Masks made no effective difference, protecting 74% of negatives and failing to protect 71% of positives. However the next sentence in the report is important:
Close contact with one or more persons with known COVID-19 was reported by 42% of case-patients compared with 14% of control-participants (p<0.01), and most (51%) close contacts were family members.
As one might expect, the got the COVID from a close contact at home where it's safe to say nobody had a mask on.